A storetank supplying powder which discharges powder particles contained therein in a constant amount is widely used in powder coating epuipment as can be found in, for example, Japanese Patent Disclosure Heisei 4-371249. Briefly explaining the storetank described therein, the tank has a separating wall disposed at a distance above a floor surface and is separated thereby into a first chamber and a second chamber thereby on its left and right, respectively. The first chamber is adapted for fluidizing the powder particles therein by ejecting air from its floor surface. The second chamber is a settling chamber in which the powder particles transported from the first chamber are left to settle, thereby removing air mixed with the powder particles. The storetank is provided with equipment, such as a screw type transporting apparatus, which forces the delivery of the powder particles within the settling chamber to the outside of the chamber.
As for other types of storetanks for the supply of powder, a venturi type of system which ejects the powder particles from the tank by utilizing fluid pressure and a bin discharger type of system which ejects the powder particles by gravitational movement of the powder particles are known.
The venturi type of system is comprised of a tank for storing the powder particles in a liquidized state, a pipe for discharging the powder particles which is inserted into the tank, and a venturi mechanism connected to the pipe. It is adapted for sucking out the powder particles within the tank by utilizing negative pressure generated by the venturi mechanism. The bin discharger type of system is comprised of a tank having an outlet at an outer periphery portion of its bottom wall, a canopy positioned above the outlet of the tank, and a rotary table disposed at the center of the bottom portion of the tank. The rotary table is provided with a plurality of vanes on its outer peripheral surface, which radially extend to a side wall of the tank and which are equiangularly spaced with respect to each other. The rotary table allows the powder particles to enter into the spaces between the vanes by falling through the outlet.
This type of storetank for the powder supply has a problem of caking and blocking of powder particles, that is, aggregation of the powder particles which are discharged from the tank. If there is a clog in the discharged powder particles, it can cause subsequent clogging. With respect to this problem, although the venturi type tank described above is advantageous, a large amount of air is necessary since it is designed to fluidize all of the powder within the tank. In addition, since it is configured to suck out the powder particles within the tank by the venturi mechanism, a large amount of air is also necessary to generate a strong suction force within the venturi mechanism.